The present invention generally relates to an apparatus useful in flameless atomic absorption spectroscopy and, in particular, relates to such an apparatus including means for the radiant heating of a sample.
In a prior art apparatus, for example, an apparatus as described in U.S. patent application ser. no. 239,934, filed on Mar. 3, 1981, a wire helix of temperature-resistant, electrically conducting material, such as tungsten, serves as a sample carrier. In use, a liquid sample is applied to the sample carrier. The sample carrier is provided with electric connections whereby it can be heated in a controlled manner by passing an electric current therethrough. Thus, the liquid sample can be dried and thermally decomposed external to the graphite tube by heating the sample carrier. The "heating device" includes the sample carrier itself acting as a resistor in combination with the electrical connections and the power source.
The known arrangement does, however, have some drawbacks. For example, only relatively small liquid sample quantities can be applied to the wire helix. In addition, the use of solid or powdery samples is not possible.
Furthermore, the sample is essentially heated in a non- uniform way; that is, heating first at the physical contact interface of the sample liquid and wire helix. Thus, the risk of sputtering of sample liquid is always present. Furthermore, the useful life of the heated wire helix is reduced because carbide formation occurs at the surface thereof.
In the prior art, a sample is occasionally introduced into a graphite crucible and inserted into a graphite tube wherein it is heated. Such heating is arranged to be independent of the graphite tube. The independent heating of the crucible inside the graphite tube entails all of the disadvantages mentioned in the above referenced U.S. patent application, which application is incorporated herein.